This invention relates to thermosettable resin compositions. In one aspect, the invention relates to bismaleimide resin compositions having improved composites laminating properties.
Bismaleimide resins are thermosettable materials useful in high-temperature electrical and structural applications. Bismaleimides are known to have excellent high-temperature properties but have been found difficult to process in applications requiring impregnation of a fibrous substrate with the resin, as is necessary for electrical and structural composites applications. The processing difficulties are to some extent the result of the limited solubility of bismaleimides in conventional organic solvents. Problems associated with such processing and solubility difficulties include inconsistent cure behavior and excessively long cure times, resulting in laminates prepared from unmodified bismaleimides which have poor copper adhesion and after-cure brittleness.
Bismaleimide resins have been modified with epoxy resins to improve processing characteristics. In such bismaleimide/epoxy compositions, it is necessary to provide a curing agent for the epoxy resin. Aromatic amines have been used as curing agents in epoxy-modified bismaleimide compositions, but such aromatic amine-cured systems have curtain property weaknesses for electrical laminating applications. For example, such systems lack long-term stability, resulting in short shelf life for the resin solutions, difficulty in establishing operational conditions for preparing prepregs and inconsistent properties in the final laminates.
It is therefore an object of the invention to provide high-temperature bismaleimides resin compositions having good processability and stability for laminating and composites applications.